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Background: Reports of whale sharks (Rhincodon typus) in the northern Gulf of Mexico (GOM) date back to the 1930s. In 2003, the Northern Gulf of Mexico Whale Shark Research Program was established and began making directed efforts to document the regional occurrence, seasonal distribution and habitat preferences of whale sharks. Methods: Whale shark sightings data (WSS: 1989 – present; n=644) and tagging geoposition data (TD: 2009-2012; n=450) were used in seasonal kernel density (KD) analyses to delineate home range (95%) and core habitat (50%) use areas in the northern GOM. Kernel density estimation of distribution is a statistically robust manner of handling data sources with differing sampling designs (anecdotal vs. directed). Habitat use patterns from the two datasets were used to identify critical use areas. Results: In the study area, whale shark home range was 276,000 km2 (WSS) to 369,000 km2 (TD) in size, with 52,000 km2 (WSS) to 62,000 km2 (TD) being core habitat. Whale shark habitat use varied seasonally, with the largest home range occurring during summer (WSS: 213,000 km2) and fall (TD: 221,000 km2). Tag data revealed more winter habitat (75,000 km2) than the sightings dataset (41,000 km2), which was shifted further offshore to slope waters. Significant use patterns occurred along the continental shelf-edge, encompassing shelf-edge banks south of Louisiana, and near the mouth of the Mississippi River. Conclusions: The combination of sightings data and satellite tagging data represents an effective methodology for assessing seasonality of occurrence, distribution, and habitat use of whale sharks. Shelf-edge bank habitats were most commonly used by whale sharks in the region. Satellite tagging data provided additional evidence of connectivity between multiple jurisdictions, which lends support for international management of the species.

Background: The Northern Gulf of Mexico Whale Shark Research Program was initiated in 2003 to increase our knowledge of whale shark occurrence and distribution within the region. A primary goal was to obtain sightings data from “citizen scientists” to guide directed research. Whale sharks are typically solitary animals, but are known to aggregate in areas of high prey abundance. Methods: Whale shark sightings data reported from 2003 to present were compiled. Aggregations were defined as more than one whale shark, and large aggregations were defined as 10 or more sharks, observed at a specific location at the same time. Efforts were made to encounter aggregations to determine size and sex assemblage of the sharks, and to collect plankton samples to identify potential prey. Results: To date we have over 600 whale shark sightings reports and four research encounters of large aggregations. Whale shark aggregations represented 31% of reported sightings, 25% of which were large aggregations between 10-150 individuals. All of thereported large aggregations occurred during summer, almost exclusively along the continental shelf edge, with 41% occurring at Ewing Bank. Three out of the four scientific encounters occurred at Ewing Bank (2009, 2010, 2013). Aggregations were dominated by immature males that were primarily feeding on Euthynnus alletteratus eggs. Conclusions: The use of sightings data provided by “citizen scientists” has proven to bean inexpensive and effective technique for identifying whale shark aggregation locations in the northern Gulf of Mexico. Aggregation assemblages appear to consist of largely juvenile males that were feeding on tuna eggs. Similar to other regions, it is unknown if whale sharks in the northern Gulf of Mexico primarily consist of juveniles or if juveniles simply dominate these large feeding aggregations.